INTERACTIONS OF POLYETHER POLYURETHANES WITH WATER-VAPOR AND WATER METHANE SEPARATION SELECTIVITY

The transport properties of water through polyether-polyurethane membranes were evaluated by absorption and permeability measurements. The state of water and the active absorption centres of the polymer were studied by FTIR. Water molecules diffuse in the polymer probably as single molecules or in clusters of very small dimensions. They can interact with polymer molecules by forming hydrogen bonds with the carbonyl group and the NH groups belonging to the urethane units and with the C-O-C groups of the ether units. Urethane-rich polymers show higher water absorption than urethane-poor polymers. The interactions are responsible for its high water solubility, while its diffusivity is ruled by the physical state of the polymer and increases even ten times from the glassy to the rubbery state. Water vapour permeability of these membranes is 10(3)-10(4) times that of methane and other permeant gases. This suggests a possible application to natural gas dehydration.